Now researchers find that large quakes might also trigger
mysterious
slow earthquakes thousands of miles away. One kind of slow
earthquake known as a slow-slip event can last for weeks,
shifting the Earth as much as an ordinary earthquake of magnitude
of 7 would in mere moments.

The investigators focused on the magnitude 8.8 Maule earthquake
that struck Chile in 2010. They found it generated surface waves
that, within hours, set off tremors in the Guerrero region of
southwestern Mexico 4,140 miles (6,660 kilometers) away. Data
from GPS stations also revealed the earth there began moving
southward at the same time tremors there began.

The tremors and movements of the GPS stations lasted for about
six months after the 2010 Chile quake.

"Such an observation may indicate that the Maule earthquake
triggered a slow-slip event in Guerrero," said researcher Dimitri
Zigone, a seismologist at the University of Southern California
in Los Angeles.

Near Guerrero lies a subduction zone, where a tectonic plate
under the Pacific Ocean is diving under the continental North
American plate. The seismic energy from Chile apparently
increased the stress in the segment of the subduction zone near
Guerrero, which may explain the resulting slow-slip event.

"The fact large quakes can have effects so far away could be
important because it may change the recurrence time between
earthquakes in a specific location," Zigone told
OurAmazingPlanet. "Usually we assume that the seismic cycle — the
recurrence between earthquakes — is regional, on a single fault
system orat a plate boundary, for example. If these large-scale
interactions exist, it may indicate that even at large distances,
a mega-earthquake can modify the conditions in another region."